orbital performance:
We expect any upper stage to use 98% peroxide + kerosene, or possibly a sodium borohydride spiked fuel for a performance boost. The mixed monoprop can get 200s Isp with a high expansion vacuum nozzle, so it would be possible to make a 3 stage orbital vehicle, but we think it would be simpler to make a single really good upper stage, rather than two simpler upper stages stages. A mass ratio of 10 for an unstreamlined, non reusable vehicle is trivial, and we actually don't think 15 will be that hard. Our opinions may change as we develop things, of course.

carbon fiber:
Carbon fiber composites have great strength, but it is better at making extremely strong things (like tanks or wing spars) much lighter than at making already light things (like our aluminum cones) even lighter. There is a significant "minimum gauge" issue, so there wouldn't be much savings in making our nosecones or cabins out of composits, and it would be much more expensive. Rolled and welded aluminum is a very cheap fabrication method, and it is much more convenient for drill and welding on the various tabs and brackets that are necessary.

multiple engines:
Our lives really did get a lot simpler when we moved from four engines to a single engine. There is a slight temptation to use multiple 12" engines because we have all the parts for them on hand, but we think it is going to be easier to just build a bigger engine instead.

1. What sort of avionics are you planning on using. I am wondering if you have installed any independant gryro instruments such as those found in general aviation aircraft. I'm thinking of these in the context of instrument that are tried and true non-digital instruments that only require power and don't rely on any computer or computerized sensors whatsoever. Something like a attitude indicator, etc.

2. Since you are having several computer failures, what have you considered for your GOne To Hell (GOTH) plan. Are you thinking of using a redundant control system, some sort of electric manual control bypassing the normal flight software, a nonballistic parachute?

3. What kind of control layout are you planning for the pilot?

_________________We fight, get beat, rise and fight again."
- Major General Nathaniel Greene

Last edited by i2blind on Mon Jul 19, 2004 9:56 pm, edited 1 time in total.

John, have you done an analysis of how the structure of the vehicle holds up under the reentry forces? Is reentry in a bottom-first orientation necessary to prevent breakup of the vehicle or can you basically throw the Black Armadillo at the atmosphere in any which way without it losing structural integrity (not even considering what this would imply for the health of the passengers)? Or is this a question that doesn't need answering, because the vehicle would be lost anyway if it was unable to orient itself correctly?

Hmm, I take back this last question, because if you are carrying passengers, being able to survive a reentry without having control authority would at least give you the opportunity to bail out after reentry. So basically, my question is simply: does the Black Armadillo allow for a care-free reentry (as Burt likes to call it)?

_________________For every complex problem there is a solution that is clear, simple, and wrong. - Henry Louis Mencken

Okay, let me just make sure I've got it. Two 12'' engines+ a ~1,000 gallon tank= one person to 100K. Four 12''ers+ a 1600 gallon tank= X Prize vehicle. Some larger reusable first stage burning monoprop+ an expendable second stage burning H2O2/Kerosene= orbit! How big would it need to be to get a human up there in orbit?

Your last update was interesting, I loved the picutre with everything laid out like it'd be in the trailer, it finally gave a decent sense of scale. I'm just wondering, what exactly are the tiny penny-size engine bells for?

_________________"Yes, that series of words I just said made perfect sense!"
-Professor Hubert Farnsworth

You've been working to improve your mass fraction, so your future vehicle's thrust-to-mass ratio will be considerably higher coming down than going up.
How deeply can you throttle your engine, and still have it work? Also, your tank pressure, and therefore thrust, will be lower on the descent than the ascent. Is this a good thing or a bad thing? How much ullage volume do you start with?

multiple engines:Our lives really did get a lot simpler when we moved from four engines to a single engine. There is a slight temptation to use multiple 12" engines because we have all the parts for them on hand, but we think it is going to be easier to just build a bigger engine instead.

have you considerd multiple engines but a single nozzle?
it would give engine out protection,increase thrust but still with only one set
of control vanes.
a three chamber design would seem the most sensible.

Abit off topic here. I read from The Register that Doom 3 has gone RTM and will be hitting the stores by next month.

Just want to say thanks for the great work. Unfortunately, I will not be getting it as my PC is too slow to run the game and I am also using a PowerBook as my laptop.

Doom had gave me great pleasures in the past. I will forever remember the times in polytechnic where we play Doom under the noses of my lecturers and the pesky technical officers those many years ago.

Hope that once this is out, you would have more time for Armadillo!

sigurd has said off topic questions are unacceptable, but seeing as there's no question involved, and it's tied in with armadillo, complements are just fine . btw, i agree completely, awesome job on doom 3, i'll probably be getting it, though that might depend on half-life 2's release date. i guess i might as well phrase it as a question, but will you be working more on armadillo once doom 3 hits stores, or will it still just be a weekend/tuesday job?

>simpler upper stages stages. A mass ratio of 10 for an unstreamlined, >non reusable vehicle is trivial, and we actually don't think 15 will be that >hard. Our opinions may change as we develop things, of course.

Still sounds like a very risky, marginal design. Say you have a 1650 gal (or is it 1600 gal?) fuel tank on the main vehicle, it weight 1700 pounds dry with a 850 gal tank, switching to 1650 gal will add 800 pounds. So we have 15000 pounds of propellant and (1700+800=2500) pounds vehicle. Engines for the liftoff weight of over 20000 pounds, so having at least 25000 lbf thrust will be over 500 lb. This is over 3000 lb of dry vehicle mass, add 10% for fuel for powered landing, it will be 3300-3400 lb. Isp is 190s.

Second stage weights, say 2000 lb, and 1/15 mass ratio.

To get a minimal total characteristic velocity of 9300-9400 m/s to get to orbit, you'll have to get vacuum Isp of second stage at 260s with 1/15 mass ratio and no payload, or 300s with 1/10 mass ratio. Both seem impossible or extremely hard to achieve... Even no "professional" upper stage has 1/15 mass ratio, Centaur B or C with a single RL/10 is a lightest one with about 1/11 or so. 300s Isp will bring extremely complex cooling problems...

Last edited by anovikov on Fri Jul 16, 2004 7:20 am, edited 1 time in total.

Hi again, John
I think that you tested some of the solid state mems type accelerometers and said they were to noisy at low G, which is why your running the fiber optic gyro. (at least that's the impression I got)
Which specific parts were those? the analog devices ADXL-202's ? There is also some brand new accelerometers out that might be worth trying.

What specs do you need from your IMU? If someone (me!) were to build an IMU with solid state accelerometers & angular rate sensors for only a couple hundred dollars or less, what specs (drift, error, frequency response) do you require? What interface would you like it to have back to your CPU? (serial, parallel, I hope not USB)?